There's no need to replace your iPhone every year. There's no need to buy the most expensive model. Apple released an iPhone SE and they sold very well. There are lots of people perfectly happy with a $200 iPhone. This idea of yearly upgrade is fine for people who want to waste their money and show off all the time, but nobody needs to do it. Apple would sell you a $5,000 iPhone if they could build it, but the only people buying $800 phones are those that want to, not those who need it.
I'm upgrading to an iPhone 7, but I've had my 5s for about three years. It still works very well.